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Background

For a certain software (Solidworks PDM) that uses a database and file archive, it is recommended to store the database on a RAID 1 disk array and the file archive on a RAID 5 disk array.

Questions

If I have an array of four disks and a hardware RAID controller, is it possible to partition each of the four disks into two partitions and use the first partitions for the RAID 1 disk array and the second partitions for the RAID 5 array? Or is it necessary that the RAID 1 and RAID 5 disk arrays use two separate sets of physical disks?

If it is possible, one set of disks would save costs compared to two sets, while providing the same level of redundancy. Can this be a reasonable setup or would mixing the two different RAID levels result in excessive loss of performance?

My research so far

I tried to search the Internet for an answer. The result which I found most closely related to my question is this post in a Dell forum. Unfortunately the answer contains abbreviations that I don't know and I was not able to grasp much of its meaning.

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  • Ask yourself why it's recommended to store the database on a RAID-1 volume (hint: it's not for optimizing disk space but read/write performance). Combining two types of workload on a small number of physical disks will probably not be good for performance. You might be better off creating one single RAID10 volume, sacrificing a bit of disk space but keeping optimal performance.
    – StarCat
    Commented Aug 19, 2020 at 14:41

1 Answer 1

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Short answer, Yes, this is perfectly possible, both on software and hardware arrays.

It is even possible to have a 2 disk setup, each 1 TB of space, creating 1 partition of 200 GB on both drives in mirrored mode (raid 0), then use the remaining space of both drives to create a striped (raid 1) partition of 1.6 TB.

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  • How on earth would you create a RAID-5 (N+1 redundant) volume with only two disks? And what would be the point? I don't think what you described is generally possible with all setups (especially not with simpler hardware RAID controllers).
    – StarCat
    Commented Aug 19, 2020 at 14:48
  • @StarCat ah... I had the wrong raid numbers. Good call. Edited the post to change it to raid 0 and raid 1. Raid 5 requires more disks obviously, but the situation is the same. As for the setup, I haven't seen a raid controller that could not do this.
    – LPChip
    Commented Aug 19, 2020 at 15:00
  • I have seen RAID controllers that could not do this, but those were older ones.
    – StarCat
    Commented Aug 19, 2020 at 15:05
  • @StarCat 25 years or so ago, I had a motherboard that had 2 raid controllers, one could do it, the other one couldn't. Not sure why that existed though... Nowadays, they are all fancy and can usually do it.
    – LPChip
    Commented Aug 19, 2020 at 15:22
  • My experience is mainly with Server class RAID card with independent controllers and onboard cache, or external storage systems. They now all have this feature but 10-12 years ago many would not.
    – StarCat
    Commented Aug 19, 2020 at 17:36

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